From 7cf404d096b02cf54d1816b2b3c83bf02b44ccd8 Mon Sep 17 00:00:00 2001
From: Kohei Takahashi <flast@flast.jp>
Date: Fri, 13 Nov 2015 21:49:27 +0900
Subject: [PATCH] SFINAE expression obstructs compile on MSVC 8.

---
 .../boost/fusion/algorithm/iteration/detail/fold.hpp  | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/boost/fusion/algorithm/iteration/detail/fold.hpp b/include/boost/fusion/algorithm/iteration/detail/fold.hpp
index c8095ae9..947c409d 100644
--- a/include/boost/fusion/algorithm/iteration/detail/fold.hpp
+++ b/include/boost/fusion/algorithm/iteration/detail/fold.hpp
@@ -42,6 +42,12 @@
 #   define BOOST_FUSION_FOLD_IMPL_INVOKE_IT_TRANSFORM(IT) fusion::deref(IT)
 #endif
 
+#if BOOST_WORKAROUND(BOOST_MSVC, < 1500)
+#   define BOOST_FUSION_FOLD_IMPL_ENABLER(T) void
+#else
+#   define BOOST_FUSION_FOLD_IMPL_ENABLER(T) typename T::type
+#endif
+
 namespace boost { namespace fusion
 {
     namespace detail
@@ -57,7 +63,7 @@ namespace boost { namespace fusion
 
         template<typename It, typename State, typename F>
         struct BOOST_PP_CAT(result_of_it_,BOOST_FUSION_FOLD_NAME)<0,It,State,F
-          , typename boost::enable_if_has_type<typename State::type>::type
+          , typename boost::enable_if_has_type<BOOST_FUSION_FOLD_IMPL_ENABLER(State)>::type
 #if BOOST_WORKAROUND(BOOST_MSVC, < 1500)
           , true
 #endif
@@ -75,7 +81,7 @@ namespace boost { namespace fusion
                 // workaround won't work with MSVC 9.
                 typename boost::disable_if_c<SeqSize == 0, State>::type::type
 #else
-                typename State::type
+                BOOST_FUSION_FOLD_IMPL_ENABLER(State)
 #endif
             >::type
 #if BOOST_WORKAROUND(BOOST_MSVC, < 1500)
@@ -236,6 +242,7 @@ namespace boost { namespace fusion
 }}
 
 #undef BOOST_FUSION_FOLD_NAME
+#undef BOOST_FUSION_FOLD_IMPL_ENABLER
 #undef BOOST_FUSION_FOLD_IMPL_FIRST_IT_FUNCTION
 #undef BOOST_FUSION_FOLD_IMPL_NEXT_IT_FUNCTION
 #undef BOOST_FUSION_FOLD_IMPL_FIRST_IT_META_TRANSFORM